1. Field of the Invention
The invention relates to a two-reel tape cartridge wherein an elastic belt is entrained around the tape packs to drive the tape tangentially.
2. Description of the Related Art
Coassigned U.S. Pat. No. 3,692,255 (Von Behren) discloses a two-reel tape cartridge in which an elastic belt is driven by a reversible motor to drive the tape bidirectionally. The belt is stretchably entrained around the tape packs, a belt driving roller, and a pair of idler rollers (e.g., belt guide rollers 21 and 22 of FIGS. 1-2) that are journalled on stationary pins in the corners of the cartridge. A predetermined frictional coupling between the idler rollers and their pins applies a predetermined drag to the belt so that the belt drives the tape faster at the take-up pack than it does at the supply pack, thus applying tension to the tape and taking up any slack that might otherwise develop in the tape between the reel hubs.
Because tape cartridges of the Von Behren patent are used for recording data, they are commonly called "data cartridges." They are currently in widespread use on devices that drive the tape at speeds from 30 inches per second (0.8 m/sec), to more than 100 inches per second (2.5 m/sec). Substantially higher tape speeds would require increased drive motor power and involve a tendency for slippage due to air entrapment between the belt and the convolutions of tape. These increased demands would encroach on the margins for safe operation of the cartridge. Furthermore, the higher ambient heat generated by increased motor sizes and drag at the idler rollers could expose the belt to higher temperatures, thus shortening its useful life.
In a second type of belt-driven, two-reel tape cartridge, frictional drag is reduced by avoiding the use of journalled idler rollers. Instead, a floating roller is squeezed against the belt and the peripheral surfaces of the tape packs. See, for example, U.S. Pat. Nos. 3,907,230 (Merle); 4,146,194 and 4,209,144 (both Majicek); and 4,205,808 (Hartig et al.). In discussing the Merle patent, Hartig says that the floating roller tends to be unstable, thus inflicting instabilities in the belt which in turn inflicts instabilities in the tape. Hartig's solution is to taper the surface of the floating roller to form a frusto-conical shape such that the belt tends to climb to the upper lip of the floating roller.
While also discussing the problem of stabilizing the position of the floating roller, the Majicek patents say that prior belt-driven cartridges of the second type could not rapidly accelerate and decelerate the tape, and that this can be alleviated by employing a belt which is thin enough and sufficiently inelastic against compression that the pressure of the floating roller compresses the tape packs as well as the belt. The Majicek '194 patent employs a floating roller, the width of which is less than the width of the belt, thus helping to stabilize the position of the floating roller. The Majicek '144 patent employs a floating roller that has a rigid periphery and a belt that is thin and inelastic enough to permit the floating roller to press the belt into the tape packs to deform them to produce an appreciable portion of the tape tension.
Although belt-driven, two-reel tape cartridges of the second type were introduced to the market several years ago, they have yet to demonstrate commercial viability.